The unit of measurement aptly named the “foot” has existed since early times, with most sources crediting King Henry I of England making a decree that his foot shall become the standard for measurement.
No matter where the definition of the foot came from, it has varied slightly throughout history. The origin of the meter (or metre, as it’s known worldwide) also has a variety of beginnings. The most established story starts from John Wilkins, an English philosopher, who published in 1668 what he described as a new standard of measurement based upon the length of a pendulum that swings approximately 38 inches across in one second. This length was eventually named the meter by an Italian scientist.
Another century later, King Louis XVI of France issued a integration law establishing the modern metric system with weights and measures having a base-ten system of units and sub-units. Within this system was the meter with a new length definition of being one ten millionth (1/10,000,000) of the distance from the North Pole to the Equator.
Upon completion of the calculations, a rectangular bar made of platinum and iridium was created to establish the “standard” meter from which all future measurements would be based.
The United States first recognized in 1866 the metric system and the meter (set forth as one meter equaling 39.37 inches). During this time, the International Commission of the Meter officially adopted the physical meter bar as the standard.
Over the next 100+ years, many studies were undertaken to re-establish the length of the meter. Using wavelengths of various elements, including cadmium, mercury, neon, zinc, helium, thallium and krypton, new definitions were created. In 1983, the current definition of the length of the meter was finalized.
The meter is now based upon the speed of light in a vacuum (299,792,458 m/s) with the meter being the length traveled in 1/299,793,458 of a second. While the length is very close to the original measurements set forth over the centuries, it is better defined for reproduction worldwide without having to possess a standard bar or other device.
To further muddy the standardization of units, in 1959 an international agreement was made by Australia, Canada, New Zealand, South Africa and the United Kingdom so one yard would equal 0.9144 meters. Meanwhile, the U.S. National Bureau of Standards published a notice that all survey-related measurements will remain based so one one yard equals 3600/3937 meters or 0.91441083 meters.
Image: NGS Source : https://www.gpsworld.com/datums-feet-and-gnss-vectors-the-2022-ngs-upgrade/
